let ul = document.querySelector('.content').getElementsByTagName('ul')
let btn = document.querySelector('.container_btn').getElementsByTagName('button')
for (let i = 0; i < btn.length; i++) {
    btn[i].onclick = function () {
        for (let j = 0; j < ul.length; j++) {
            btn[j].className = null
            ul[j].className = null
        }
        this.className = 'btn_active'
        ul[i].className = 'active'
    }
}